1. Field of the Invention
The present invention relates to a rotating fluid machine including a casing, a rotor rotatably supported at the casing, a working part provided at the rotor, and a rotary valve provided between the casing and the rotor to control supply and discharge of a working medium to and from the working part.
2. Description of the Related Art
Japanese Utility Model Laid-Open No. 61-155610 discloses a rotating fluid machine for supplying a combustion gas generating in a combustor to an axial piston cylinder group via a distributing mechanism (rotary valve), in which a pressing member is pressed with a spring to bring the pressing member into close contact with a slide surface when the combustion gas is not supplied, and the pressing member is pressed via a free piston with pressure of the combustion gas to bring it into close contact with the slide surface when the combustion gas is supplied, thereby securing the sealing performance of the slide surface of the distributing mechanism (valve seat).
A small swing occurs to the rotor, which is supported at the casing with ball bearings, during rotation, and therefore it is inevitable that swing also occurs to the slide surface of the rotary valve. At this time, it is difficult to secure sealing performance with the pressing member following the swing of the slide surface by only biasing the pressing member with a resilient force of the spring, pressure of the combustion gas, pressure of a supply gas at high temperature and high pressure or pressure of steam to bring the pressing member into close contact with the slide surface.
In a rotary valve for an expansion machine, it is considered to form a pressure chamber open to a mating surface with the fixed side valve plate in a valve body portion and make the pressure of the working medium act on a back surface of a seal member having flexibility, such as a V-packing, housed in the pressure chamber, to thereby press the fixed side valve plate against a movable side valve plate to secure the sealing performance of the slide surface.
However, when the pressure of the working medium does not rise sufficiently just after the start of the expansion machine, the seal member cannot exhibit the sufficient sealing function due to insufficient pressure, and if a foreign matter such as an oxidized scale is contained in the working medium, the seal member is damaged, and the sealing performance is further reduced, which brings about the possibility that the expansion machine cannot exhibit sufficient performance.
The movable side valve plate provided at the rotor inevitably oscillates a little. If the fixed side valve plate in contact with the movable side valve plate via the slide surface oscillates, there is the possibility that the close contact of a seat surface of the fixed side valve plate and a lip of the seal member is impaired and steam leaks out of this portion to make it impossible for the expansion machine to exhibit sufficient performance.
When the pressure of the working medium supplied to the pressure chamber is low, the outer periphery surface of the V-packing cannot be firmly pressed against an inner periphery surface of the pressure chamber, and the working medium sometimes leaks out of the pressure chamber due to reduction in the sealing function. Once this leakage occurs, the leakage cannot be stopped even if the pressure of the working medium increases, and therefore it is necessary to stop the operation of the expansion machine and restart it thereafter. In order to solve these problems, it can be considered to enhance sealing performance by pressing the V-packing in the axial direction with coil spring. However, since it is difficult to bias the V-packing outward in the radial direction with the coil spring placed in the axial direction and the resilient force of the coil spring reduces when the working medium is at high temperature, a sufficient effect cannot be expected.